R/ud_convert2.R

In ashiklom/hector-rcmip: Hector RCMIP 2019 helpers

#' Chemical symbol-aware unit conversion
#'
#' @param x Numeric value to convert
#' @param from,to Units from/to which to convert. Syntax is identical to
#'   [udunits2::ud.convert()] except that chemical symbols in hard brackets
#'   (e.g. `[N2O]`) can be converted.
#' @return Values of `x` converted to `to` units.
#' @author Alexey Shiklomanov
#' @export
#' @examples
#' ud_convert2(5, "Pg [C]", "Mt [CO2]")
#' #> 18.32223
ud_convert2 <- function(x, from, to) {
  udunits2::ud.convert(x, parse_chem(from), parse_chem(to))
}

parse_chem <- function(unit) {
  unit2 <- unit
  rx <- "\\[.*?\\]"
  m <- regexpr(rx, unit2)
  while (m != -1) {
    regmatches(unit2, m) <- sprintf(
      "(1/%f)",
      get_molmass(regmatches(unit2, m))
    )
    m <- regexpr(rx, unit2)
  }
  unit2
}

get_molmass <- function(s) {
  biogas::molMass(gsub("\\[|\\]", "", s))
}